Spraying for dust suppression is a conventional technological means for industrial dust control. The traditional spraying technique shows a few shortcomings, including low dust suppression efficiency, great water consumption, and failure in far-distance dust suppression. This study proposed a novel combined spraying dust suppression device and established the related physical model and mathematical model. Using the CFD numerical simulation method, the basic characteristics of the airflow field and spray field around the device and the related influencing factors were investigated in depth. Results showed that the Coanda effect appeared near the wall surface in the air duct when the combined spraying dust suppression device was operated. Under this effect, negative pressure formed at the center of the device. The velocity of the combined device showed a symmetrical distribution and decayed steadily downward from the outlet of the device. An obvious stratification can be observed in the spray field. The mean droplet size first increased and then decreased along the airflow direction. Meanwhile, the effects of the air supply pressure and water supply pressure were examined. On the one hand, the velocity of the combined spraying dust suppression device and the spraying range were in direct proportion with the air supply pressure. As the air supply pressure increased, the droplet size first increased and then decreased. On the other hand, increasing the water supply pressure imposed almost no effect on the airflow field of the combined spraying dust suppression device but can reduce the droplet size and enhance the spraying range.

As a new type of atomizing nozzle with superior atomizing performance, the liquid-medium ultrasonic atomization nozzle has been widely applied in the field of spray dust reduction. In this study, in order to establish a mathematical model for predicting the Sauter mean diameter (SMD) of such nozzles, the interaction between the SMD of the nozzle and the three influencing factors, i.e., air pressure, water pressure, and outlet diameter were investigated based on the custom-designed spraying experiment platform and orthogonal design methods. Through range analysis, it was obtained that the three parameters affecting the SMD of the nozzle are in the order of air pressure > water pressure > outlet diameter. On this basis, using the multivariate nonlinear regression method, the mathematical model for predicting the SMD of the nozzle was constructed. Comparison of the experimental results with the predicted values of the SMD of the nozzle by the multivariate nonlinear regression mathematical model, showed strong similarity with an average relative error of only about 5%. Therefore, the established mathematical model in this paper can be used to predict and calculate the droplet size for liquid-medium ultrasonic atomizing nozzles.

Coal dust is a major safety hazard in the process of coal mining and is of great importance to ensure production safety and maintain the health of operators. In order to understand the microscopic mechanism during coal seam water injection and reveal the mechanism of surfactants in improving the wettability of coal dust, coking coal was selected as the research object. Three surfactants, SDBS, AEO-9, and CAB-35, were chosen for molecular dynamics simulation research on the wetting and adsorption properties of water/coal/surfactants. The results show that surfactant molecules can cover the hydrophobic groups on the surface of coking coal, forming a hydrophilic adsorption layer, changing the coal surface from hydrophobic to hydrophilic, and enhancing the wettability. After adding surfactants, the thickness of the adsorption layer in the z-axis direction increases, expanding the contact area between coking coal and water molecules, thereby improving the wettability. When surfactants tightly cover the surface of coking coal, their binding strength increases, forming a more stable hydrophilic layer and further improving the wettability. At the same time, surfactants promote the diffusion of water molecules and enhance the interaction between hydrophobic alkyl chains and water molecules, further enhancing the wetting effect.

The circular-hole rotating core fog nozzle has excellent atomization performance and has been widely used in the realm of spray dust. As part of this study, a mathematical model was developed for predicting the Sauter mean diameter (SMD) of nozzles of this type. The coaction between the SMD of the nozzle and the three influencing factors of axial distance, water supply pressure, and outlet diameter was investigated based on the customized spray’s experimental platform and orthogonal design method. According to the comparative analysis of the size range, the axial distance, outlet diameter and water supply pressure are three parameters that affect the SMD of the nozzle, and the degree of influence is axial distance > outlet diameter > water supply pressure. On this basis, a mathematical model was developed using the multiple regression method to predict the SMD of the nozzle. We analyzed the results and compared them to the SMD value predicted by the multiple regression mathematical model and the orthogonal experiment results. The change trend was the same, the values were essentially the same, and the average relative error was just 16.11%. Accordingly, the mathematical model presented in this paper may be used for the prediction and calculation of the droplet size for circular-hole rotating core micro-fog nozzles.